Severe hypertension, tachycardia or ECG changes have been reported following i.v. administration of pancuronium to patients with pheochromocytoma or bronchial asthma. These cardiovascular changes were explained by an interaction between autonomic effects of pancuronium and elevated serum catecholamines or aminophylline. We noted similar cardiovascular changes associated with i.v. administration of pancuronium in two patients after successful cardiopulmonary resuscitation and in two with midbrain hemorrhage and epidural hematoma. In these patients, pancuronium produced no abnormal cardiovascular changes when given during elective surgery or before the occurrence of midbrain hemorrhage. Thus, ischemic brain damage may play a role in producing the severe cardiovascular changes associated with pancuronium.